Despite being heavily outspent by brewing magnate Pete Coors in the run-up to Tuesday’s Senate Republican primary in Colorado, former Rep. Bob Schaffer’s allies believe he is within reach of pulling off a major upset.

A Mason-Dixon survey conducted for the Denver Post suggested that the contest is indeed close.

The survey, released Friday, gives Coors a narrow 45 percent to 41 percent margin over Schaffer. Among “definite” voters, Schaffer actually led, 46 percent to 45 percent.

“We are confident about where we are,” said Schaffer campaign manager Pat Fiske. “There are enough undecideds that the race is not over.”

Although he will not run a single television or radio advertisement in the primary, Schaffer’s prospects have improved in recent weeks thanks to spending by Colorado Conservative Voters, a soft-money group whose radio and television ads have attacked Coors.

“When you get right down to it, all I am doing is pitching in to try and even the odds,” said former Sen. Bill Armstrong (R-Colo.), the head of CCV.

Cinamon Watson, a spokeswoman for the Coors campaign, countered by calling the CCV ads a “smear campaign,” adding, “Pete is definitely going to win.”

Watson did acknowledge, however, that “some of the negative attacks launched by Sen. Armstrong and his third-party group will have some impact.”

The seat is being vacated by two-term Sen. Ben Nighthorse Campbell (R). While the Republican Senate primary has drawn the most attention in the state, Democrats are hosting a primary of their own between state Attorney General Ken Salazar and educator Mike Miles.

Miles scored a huge upset at the June party convention when he defeated Salazar to claim the top spot on Tuesday’s ballot. But almost no one expects a repeat of that performance.

Cody Wertz, a spokesman for Salazar, said after the convention defeat “there is a definite buzz that we need to get our voters out.”

“They know they can’t take anything for granted,” Wertz said.

In the Mason-Dixon survey, which was conducted Aug. 2-4, Salazar held a commanding 67 percent to 21 percent lead over Miles.

Salazar had raised in excess of $2.9 million for the race as of July 21 and had $1.7 million on hand.

Miles had brought in just $323,000 with $40,000 in the bank by then.

Salazar “has more money. He can buy more television ads,” said Miles spokeswoman Liz Gauthier. “We have Coloradans all over the state who have approached this campaign like a second job.”

Among House races, only the 3rd district seat being vacated by six-term Rep. Scott McInnis (R) is hosting a truly competitive primary.

While state Rep. John Salazar has cleared the Democratic field for the Western Slope seat, five Republicans are seeking to replace McInnis with former Department of Natural Resources Secretary Greg Walcher, the frontrunner.

Nationally, the seat is one of roughly 35 seats that will be hotly contested by the parties this fall.

Still, for now all eyes in the state are on the battle between Coors and Schaffer — a clash that many are casting as a fight for the ideological soul of the party.

During his 10 years in the state House from 1986 to 1996, Schaffer developed a reputation as one of the most conservative members of that body. He cemented that image during his six years in Congress, leaving his 4th district seat in eastern Colorado due to a self-imposed term-limits pledge in 2002.

Coors, in his first run for political office, has highlighted his background as a successful businessman who’s able to get results, drawing a contrast with the more ideologically pure — and, to Coors supporters, less effective —approach taken by Schaffer.

The chief political patrons of the two men illustrate the divide between Coors and Schaffer.

Coors was urged into the race by Gov. Bill Owens, the head of the state’s GOP establishment. Though conservative in beliefs, Owens projects a moderate image and is mentioned as a possible presidential candidate in 2008.

The Coors campaign is currently using Owens’ endorsement in an automated phone call to voters. The governor is also expected to stump with his hand-picked candidate throughout the state today.

Armstrong, on the other hand, sees himself as a citizen legislator who’s ready to prioritize ideology over politics.

The fundraising numbers posted by Armstrong’s CCV reveal that he is putting much more than rhetoric behind his support of Schaffer.

As of July 27, Armstrong had donated $100,000 from his own pocket to the effort, as did 1992 Senate candidate Terry Considine (R) and wealthy communications executive John Saeman.

Because CCV is classified as a 527 organization under the federal tax code, it may accept unlimited donations from individuals but must report its contributions and expenditures with the Internal Revenue Service and Federal Election Commission.

According to those reports, the group has spent upwards of $350,000 on a television campaign designed to question Coors’ conservative credentials.

Schaffer, by contrast, had spent $629,000 through July 21 but had not devoted a dime to paid television or radio communications.

The CCV ads allege that Coors, as head of the brewing company of the same name, supports the “homosexual agenda” as well as lowering the drinking age from 21 to 18.

The group has concentrated its ads in the Colorado Springs media market, the most Republican and socially conservative area of the state.

The effect is already apparent in internal polling conducted for CCV. Those surveys indicate that Schaffer went from being “disastrously behind” in Colorado Springs on July 13 to ahead in a similar survey conducted a week ago, Armstrong said.

Those gains may be eroded somewhat by Rep. Joel Hefley’s (R-Colo.) endorsement of Coors. Hefley represents the 5th district, which includes Colorado Springs.

Schaffer’s winning formula is centered on carrying Colorado Springs, running up a huge margin in his old 4th district and trying to hold down Coors’ margins in metropolitan Denver and the Western Slope.

CCV began running ads Thursday on cable television in both the Grand Junction and Denver media markets in a bid to limit Coors’ vote totals.

Even with those efforts, Schaffer’s most optimistic backers admit that Coors is drastically outspending them on television and remains the favorite in the race.

Coors had raised $2.6 million for the contest through July 21, a total that included a $400,000 personal donation.

“Pete’s ability to raise money speaks to the support and momentum of the campaign,” said Watson.

He has spent more than $1 million on an extended media campaign designed to introduce him as a politician to voters accustomed to seeing the tall, white-haired Coors on television plugging his beer with the Rocky Mountains as the backdrop.

After Armstrong’s group began attacking Coors, his campaign struck back with an ad alleging that Schaffer had “padded his résumé” by claiming to be the president of a bank that had not yet come into existence.

“We probably put more [money] into the race than we had initially expected,” said Watson. “We have had to respond and spend additional funds.”